Diets: Four Ways Not to Lose Weight

When diets fail, we're apt to blame the chips we couldn't stop eating or those decadent desserts. But high-calorie treats don't deserve all the blame. Turns out many of the foods dubbed "healthy" or "diet" may also be culprits. Everything from diet soda to a "light" entree can cause you to gain weight or consume more calories. The explanations are a bit complicated (how can diet soda actually increase the likelihood that you'll become overweight?), but recent studies have established a link, and it's enough to make anyone looking to lose weight think twice before buying popular low-cal products for themselves or their families. A look at four diet tactics that can backfire:

1. Ordering "Healthy": You think you're doing the right thing by ordering the diet plate or a main dish labeled "healthy" on a restaurant menu—maybe the steamed veggies and fish instead of the steak. But that calorie-pinching main dish may have a negative effect on the rest of your meal. A study in the July issue of the Journal of Consumer Research found that consumers consume beverages, side dishes and desserts containing up to 131 more calories when the main dish is advertised as healthy. Basically, we feel entitled to a reward if we feel we've deprived ourselves. After all, how can a few cookies hurt after we've skimped on the entree, the thinking goes. And don't assume that something labeled healthy is low-cal. When participants in the Consumer Research study had to guess how many calories were in a sandwich, they estimated that sandwiches contained 35 percent fewer calories when they came from restaurants that made health claims, even if the calorie differences aren't actually there. Experts say it's often better to order a balanced but filling meal, if it means you'll feel full and skip those empty calories later.

2. Drinking Diet Soda: Many of us are loud and proud about our Diet Coke addictions—Bill Clinton, Elton John and Victoria Beckham included. But as thin as Mrs. Beckham might be, don't assume that drinking diet is a diet in and of itself. In fact, it might just be the opposite. Research from the University of Texas in 2005 found the consumption of diet soda actually increased an individual's chance of gaining weight. And the numbers are staggering—for each can of diet soft drink consumed each day, a person's risk of obesity went up 41 percent, and his or her chance of being overweight went up by 65 percent. What does drinking something that's calorie-free have to do with being overweight? Researchers don't quite know, but there are two elements they think may be at play: either individuals are prompted to drink diet soda because they are already heavy and want to lose weight, or they think a diet soda is a diet in itself—so they go to McDonald's and order a Big Mac, large fries, and a Diet Coke. The diet drink by no means balances the heavy calorie consumption. That's not to say you should be drinking a giant, 40-ounce sugary soda instead of the diet version and ordering a huge meal. Bottom line: if you're interested in losing weight, water is your best bet beverage.

3. Going for the "Low Glycemic Index" Label: The glycemic index (GI) ranks carbohydrates by how they alter blood glucose levels and how fast they break down in your digestive system. Foods that have a high GI are thought to be "bad carbs" because they cause a spike in blood sugar; those with a low GI are the good guys because they are slower to break down, keeping you satiated longer—which dieters hope will promote weight loss. GI indicators have become popular fixtures on protein bars and snack foods like "low-carb" cookies. But two studies, one from the University of Virginia and the other from Tufts, have found that measures of GIs can be extremely variable from person to person, and they depend on what else you might be eating at the same time. The Tufts study, for example, found that a simple piece of white bread had different GIs for different people; in some it would cause a spike in blood sugar and in others it would not. A newer study out of Virginia analyzed hundreds of studies on GI and found no significant health or weight differences between people eating low-GI and people eating high-GI foods. Better to go for high-fiber snacks to fill up and stay healthy. (Of course, if you're diabetic you should consult your doctor about diet and how the GI of any particular food affects you.)

4. Serving Diet Products to Kids: Parents worried about their children's weight or simply aiming to keep them eating "healthy" by serving low-cal snacks may be unknowingly taking a step in the wrong direction. A study in the August issue of the medical journal Obesity found that when we eat diet foods at a young age we overeat similar-tasting foods later in life, suggesting that low-cal foods disrupt the body's ability to recognize how many calories an item contains. The data, however, is still pretty tentative—it comes from a study by the University of Alberta in Canada that was performed on rats. But the researchers' explanation is still some food for thought: it looks as though consuming a sweet, low-cal food, like sugar-free cookies or Diet Coke, stimulates our desire for sugar; when we don't get that sugar from a diet-food product we just go find it elsewhere. And this had a particularly adverse effect on the rats that were fed low-cal foods at a young age.